Mississippi Lake Water Quality

Mississippi lists 412 lakes across 78 counties, 78 of them with a recent water-quality reading. Most of that sampling flows through monitoring run by the Mississippi Department of Environmental Quality, which feeds state, federal, and volunteer measurements into the EPA Water Quality Portal. The remainder are here because they are real named lakes, not because anyone has sampled them recently. Most measured Mississippi lakes are productive, often shallow, and frequently algal in late summer; each lake page shows its own phosphorus and chlorophyll-a readings.

Sardis Lake is the largest lake in this index at about 33,218 acres, one of 42 here that clear 500 acres. The rest run smaller, and small and shallow is where nutrient loading shows up first, because there is less water to dilute it and the bottom sediment stays within reach of the sun. Eutrophic conditions dominate the measured set: nutrient-loaded, productive, with algal pressure that shows up most years in late summer. These lakes tend to be shallow, in agricultural watersheds, and over-warmed by the time July ends. The county with the lowest nutrient and algae readings on average is Prentiss. The gap between counties is large enough that a single figure for Mississippi lake water quality hides real local variation.